1. Technical Field
The present invention relates to a nitride-based semiconductor device and a method for manufacturing the same, and more particular, to a nitride-based semiconductor device and a method for manufacturing the same capable of reducing a reverse leakage current and increasing a withstand voltage.
2. Description of the Related Art
In general, a group III-nitride-based semiconductor including group III element such as gallium (Ga), aluminum (Al), and indium (In), and nitrogen (N) has characteristics such as a wide energy band gap, a high electron mobility, a saturation electron velocity, and a high thermal chemical stability. A nitride-based field effect transistor (N-FET) based on this group III-nitride-based semiconductor is manufactured by materials such as semiconductor materials having a wide energy band gap, for example, gallium nitride (GaN), aluminum gallium nitride (AlGaN), indium gallium nitride (InGaN), aluminum indium gallium nitride (AlINGaN), etc.
General nitride-based field effect transistors each include a base substrate, an epitaxial growth film formed on the base substrate, and a Schottky electrode and an ohmic electrode disposed on the epitaxial growth film. In this nitride-based semiconductors, a 2-dimensional electron gas (2DEG) used as a movement route of current is generated in the epitaxial growth film. The nitride-based semiconductor can implement forward and reverse operations by using the 2-dimensional electron as a carrier movement route.
A Schottky diode device of the above described nitride-based semiconductor devices utilizes a Schottky junction between metal and semiconductor. This nitride-based semiconductor device allows fast switching operation and driving by low forward voltage. A nitride-based semiconductor device such as the Schottky diode has a Schottky electrode for Schottky contact as an anode electrode and an ohmic electrode for ohmic contact as a cathode electrode.
However, in the Schottky diode having this structure, leakage current is generated from the Schottky electrode to the base substrate at the time of reverse operation. To prevent the reverse leakage current, a silicon substrate, a silicon carbide substrate, a spinel substrate, or a sapphire substrate, each of which has a resistance value of 1 kΩ or more, is used as a base substrate of the general nitride-based semiconductor device. However, it is impossible to fundamentally prevent the generation of the leakage current even when using of the above substrate having a high resistance value. Also, the above substrate having such a high resistance value is relatively expensive. Especially, a silicon wafer having a high resistance value of 1 kΩ or more, which is generally and widely used, is significantly expensive compared with other substrates. This causes an increase in the manufacturing costs of the nitride-based semiconductor device.